Abstracts

XX International Linac Conference

MOD19 (Oral Poster)

Evolution of the LEBT Layout for SNS*

J. REIJONEN, R. THOMAE, R. KELLER (BERKELEY LAB)

As the startup Low-Energy Beam Transport (LEBT) for the Spallation
Neutron Source (SNS) project is undergoing commissioning aimed at transporting a
35-mA H-beam, a new LEBT layout has been developed that is designed to transport a
beam current of 65 mA, consistent with the revised nominal SNS beam-power goal of 2
MW. The SNS LEBT employs two electrostatic einzel lenses and provides static beam
steering as well as fast chopping, implemented by splitting the second lens into four
quadrants. The development was carried out using the code IGUN in a novel way that
allows working with finite ion temperatures without encountering any problems. The
changes with respect to the startup LEBT layout affect electrode shapes in the
upstream part only: the downstream part is kept as previously designed, to preserve
the chopping action. In addition, the overall length was kept constant, and only
minor changes had to be made to the design of some of the support structures: the
vacuum tank design is identical to the previous one. The expected performance of this
new LEBT, based on the simulations, is described for a large range of output
Twiss-parameters and compared to simulation results for the startup
configuration.

* This work is supported by the Director, Office of Science, Office of
Basic Energy Sciences, of the U.S. Department of Energy under Contract No.
DE-AC03-76SF00098.